The field of the present invention is gasoline engines, and in particular fuel pumps for such engines.
In many small gasoline engines, such as those used to power lawn and garden equipment and electrical generators, the fuel tank is mounted above the carburetor. This allows the fuel to flow by gravity from the tank to the carburetor without the need for a pump. The fuel tank can even be mounted a small distance below the carburetor with the fuel being drawn into the carburetor by a vacuum created in the carburetor by the Bernoulli effect.
However, in some applications, the fuel tank must be located a significant distance below the carburetor where the vacuum created in the fuel line at the carburetor is inadequate to overcome the force of gravity. Since this type of gasoline engine was designed to operate without a fuel pump, provision was not made to attach a mechanical fuel pump to the engine for these applications. Such a mechanical fuel pump requires access through the engine block for a pump lever to engage the cam shaft or the crank shaft. Furthermore, since these relatively small engines do not have an electric generator, it is impractical to provide an electric fuel pump for such applications.
As a consequence, engines that were designed to function without a fuel pump heretofore could not be utilized readily with a gas tank mounted a significant distance below the carburetor.